A strongly alkaline simple thermal spring at pH 9.9. Lightly mineralized at just 0.187 g/kg of dissolved solids and gentle on the body, yet the strong alkalinity gives a pronounced slippery feel on the skin, placing it squarely in Japan's beauty-water family. At the source the water carries a faint sulfur note.
Good for
Smooth skin
Bicarbonate and alkalinity gently lift dead keratin while silica hydrates, leaving skin smooth. This is the basis of the beautifying-water (bijin-no-yu 美人の湯) reputation.
dry, rough skin
Recovery
Warmth and buoyancy lower stress markers and improve sleep; habitual bathing is linked to lower rates of depression.
fatigue, stress
Take care
From a certificate analyzed in 2017.
- acute illness, especially when feverish
- active tuberculosis
- severe heart disease
Full composition
The bar is each ion's share of charge (mval%) within its group; over 20% names the spring. Gases, silica and trace metals are measured by mass only.
- Sodiumsalt's cation — pairs with chloride to make the water saltyNa⁺57.3mgP15 national93%
- Calciumsettling and calming; can leave a white mineral bloomCa²⁺3.3mgP12 national6%
- PotassiumK⁺0.30mgP3 national0.4%
- AluminumAl³⁺0.10mgP56 national0.4%
- BariumBa²⁺0.0000mg0.0%
- Iron (II)Fe²⁺0.0000mg0.0%
- Iron (III)Fe³⁺0.0000mg0.0%
- HydrogenH⁺0.0000mg0.0%
- LithiumLi⁺0.0000mg0.0%
- MagnesiumMg²⁺0.0000mg0.0%
- ManganeseMn²⁺0.0000mg0.0%
- AmmoniumNH₄⁺0.0000mg0.0%
- StrontiumSr²⁺0.0000mg0.0%
- ZincZn²⁺0.0000mg0.0%
- Sulfate"gypsum / Glauber's salt" — vessels and wound healingSO₄²⁻44.7mgP39 national35%
- Chloridetable-salt anion — coats the skin and holds heat inCl⁻26.3mgP18 national28%
- HSiO3HSiO₃⁻43.1mgP91 national21%
- Bicarbonate"soda" — softens skin, leaves it smoothHCO₃⁻6.0mgP4 national8%
- HydroxideOH⁻0.80mgP84 national3%
- BO2BO₂⁻2.9mgP68 national3%
- Fluoridetrace; drinking limits applyF⁻0.70mgP38 national2%
- Hydrogen sulfidesulfur character — antibacterialHS⁻0.90mgP68 national1%
- AsO2AsO₂⁻0.20mgP91 national0.0%
- Hydrogen phosphateHPO₄²⁻0.20mgP52 national0.0%
- BromideBr⁻0.10mgP14 national0.0%
- HSO4HSO40.0000mg0.0%
- IodideI⁻0.0000mg0.0%
- ThiosulfateS₂O₃²⁻0.0000mg0.0%
- Metasilicic acidmetasilicic acid — a natural moisturizer for silky skinH₂SiO₃0.0000mg
- H2SO4FreeH2SO4Free0.0000mg
- Phosphoric acidH₃PO₄0.0000mg
- Metaarsenious acidHAsO₂0.0000mg
- Metaboric acidmetaboric acid — mildly antibacterialHBO₂0.0000mg
- Free carbon dioxidefizz — widens blood vessels (strong above 1000 mg/kg)CO₂0.0000mg
- Free hydrogen sulfide"egg" smell — opens vessels, antibacterialH₂S0.0000mg
- ArsenicAs0.14mgP71 national
- CadmiumCd< —mg
- CopperCu< —mg
- Mercurytoxic trace — part of the drinking-safety checkHg< —mg
- LeadPb< —mg
Measured at the source
On the certificate
From a certificate analyzed in 2017.
- chronic muscle or joint pain and stiffness
- poor circulation (sensitivity to cold)
Evidence
- Maeda M. 温泉の医学的効果とその科学的根拠. J. Hot Spring Science 70:197–207, 2021.
- Naito Y et al. A Hot-Spring Water Improves Inflammatory Conditions in an Atopic Dermatitis Model. Biomedicines 13(11):2707, 2025.
- Li H et al. Bicarbonate Ionized Water Bathing Enhances Natural Killer Cell Activity. Scientific Reports 14:51851, 2024.
- Takeda M et al. Hot spring bathing practices have a positive effect on mental health in Japan. Heliyon 9(9):e19631, 2023.